There is a continuing need in medical practice and research, and in analytical and diagnostic procedures for rapid and accurate determinations of chemical and biological substances which are present in various fluids, such as biological fluids. For example, the presence of drugs, narcotics, hormones, steroids, polypeptides, metabolites, toxins, viruses, microorganisms or nucleic acids in human or animal body fluids or tissues must be determined rapidly and accurately for effective research, diagnosis or treatment.
In approximately the last twenty years, a wide variety of analytical methods have been developed to detect the substances noted above. Generally, the state of the art has advanced to such a degree that analytical and diagnostic methods have become highly reliable and suitable for automation or for use with test kits which can be readily used in doctors' offices or at home. Most of such methods rely on what are known in the art as "specific binding" reactions in which an unknown substance to be detected (known as a "ligand") reacts specifically and preferentially with a corresponding "receptor" molecule. Most well known specific binding reactions occur between immunoreactants, such as antibodies and antigens (foreign substances which produce immunological responses), but other specific binding reactions (such as between avidin and biotin and a sugar with a lectin) are well known.
Methods in the art using specific binding reactions generally require that one or more or both of the reactants be immobilized on a solid substrate of some type, so that unreacted (and generally water-soluble) materials can then be separated from the water-insoluble reaction product (often called a "complex"). In addition, such immobilized reactants can be used in affinity chromatography to remove a desired biologically active material from a mixture of such materials.
Biologically active substances have thus been immobilized to advantage on particulate substrates such as polymeric particles, animal and human erythrocytes, bacterial cells and other solid materials known in the art. For example, carrier particles prepared from epoxy-group containing monomers are described in U.S. Pat. No. 4,415,700 (issued Nov. 15, 1983 to Batz et al). Where polymeric particles have been used as carrier substrates, biologically active substances have been attached through reactive groups on the particle surface, such groups provided either from the polymer composition or from linking moieties attached to the particles. U.S. Pat. No. 4,401,765 (issued Aug. 30, 1983 to Craig et al) describes a number of reactive groups on polymeric particles.
Several advances in the art in this regard are described in copending U.S. Ser. No. 081,206 (filed Aug. 3, 1987 by Sutton et al), now abandoned U.S. Ser. No. 136,165 (filed Dec. 18, 1987 by Burdick et al), now abandoned and EP-A-O 308 235 (published Apr. 26, 1989 and corresponding to U.S. Ser. No. 373,304, filed Jun. 29, 1989 by Sutton et al as a continuation-in-part of U.S. Ser. No. 098,429, filed Sep. 18, 1987), now abandoned. These applications describe various means for attaching biologically active substances to polymeric particles having various reactive surface groups, including surface carboxy groups, such as groups provided by acrylic and methacrylic acids.
Carboxylated latex particles have also been used to prepare diagnostic reagents, as noted in U.S. Pat. No. 4,181,636 (issued Jan. 1, 1980 to Fischer). The described particles are prepared using a carboxyl-containing monomer such as acrylic acid, methacrylic acid, itaconic acid, aconitic acid, fumaric acid or maleic acid. Similar particles are described in U.S. Pat. No. 3,857,931 (issued Dec. 31, 1974 to Hager), U.S. Pat. No. 4,138,383 (issued Feb. 6, 1979 to Rembaum et al) and U.S. Pat. No. 4,264,766 (issued Apr. 28, 1981 to Fischer).
Two commercially available monomers, 3-acrylamido-3-methylbutanoic acid and 2-acrylamido-2-hydroxyacetic acid, have been polymerized to form polymers. These monomers are generally water-soluble and are difficult to copolymerize with oleophilic monomers and are not readily polymerized to form monodisperse particles.
Another advance in the art relates to the use of specific compounds to attach biological materials to particulate substrates having reactive carboxy groups. Generally, water-soluble carbodiimides have been used, as described in the references noted above. More recently, however, carbamoylonium compounds have been used for this purpose with considerable advantages, as described in copending U.S. Ser. No. 373,304 (filed Jun. 29, 1989 by Sutton et al) as a continuation-in-part of U.S. Ser. No. 286,097 (filed Dec. 19, 1988), now abandoned which is a of U.S. Ser. No. 098,429 (filed Sep. 18, 1987), now abandoned. Dication ethers are also known to be useful, as described in copending U.S. Ser. No. 389,390, (filed Aug. 3, 1989 by Scensny and Chen).
The modification of protein adsorption on polymeric surfaces has been a common goal for many workers trying to apply polymer technology to in vivo and in vitro uses in biotechnology. Undesirable protein adsorption has been a continual problem. For example, nonspecific adsorption is a major concern in the use of polymers for affinity chromatography for the purification of proteins.
The modification of polymer surfaces has taken many forms, including physical coatings, graft copolymerization, chemical treatments and plasma gas discharge treatment. The hydrophilic nature of the polymer surface has been the subject of considerable debate and research because an increase in hydrophilicity reduces adsorption of some proteins, but not others. As noted in the art cited above, the use of reactive side chains has also received considerable attention in the art.
There is a need in the art to find new biological reagents which show improvement over the standard reagents prepared from standard carboxy-containing polymers. Such reagents would be especially useful having attached biological materials for use in research and various analytical and diagnostic procedures.